Point attack insert for rotatable cutting tool

ABSTRACT

An improved rotating cutting bit used in a road resurfacing machine, wherein the cutting bit includes a metal shank and having a forward end, and wherein the forward end includes a bore or recess that is adapted to fixedly receive at least a portion of a point attack insert. The improvement comprises a head section; an axially aligned transitional intermediate section contiguous with the head section having a first diameter, d, and a sectional height, H1; and an axially aligned base section adjacent to the intermediate section having a second diameter, D; wherein d:H1 is greater than 1.0, the ratio of d:D is from 0.62 to 0.68, wherein the point attack insert has an overall height H and the ratio of H:D is less than 0.93.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a tool for use in road resurfacing and more particularly to an improved point attack insert or tip that is received in a bore of a cutting tool that is utilized in road resurfacing.

2. Description of the Prior Art

It is known in the industry to provide rotational cutting bits having a hard alloy cap or a point attack insert mounted in a bore or recess of a metal shank. An example of such bits is described in greater detail in U.S. Pat. No. 4,497,520 issued to Ojanen on Feb. 5, 1985, the disclosure of which is incorporated herein by reference.

Typically, when in use, the bits are mounted circumferentially on a power driven cutter drum of a resurfacing machine. The resurfacing machine may have 165+ of these cutting bits mounted in an array on the drum. In the process of preparing the road surface for resurfacing, the existing surface is planed to remove a predetermined amount of road material, i.e., either concrete or asphalt. In the road preparation operation, the cutting drum is rotated at a predetermined speed and pressure so that the cutting bits engage the road surface removing the material and generally leaving a level, scored surface. During this operation, the point attack insert on each cutting bit is worn down, necessitating that the operation be temporally suspended while the cutting bits are changed-out and planing operations resumed. Replacing the cutting bits is both time consuming and involves a degree of personnel risk as the worn cutting bits are removed and new cutting bits are inserted into the drum.

U.S. Pat. No. 6,270,165 issued to Peay on Aug. 7, 2001 describes a cutting cap for rotational cutting bits. The bits have a forward end or head portion and a shank portion along a longitudinal axis and transitioning from the head portion. The head portion includes an indention, cavity or socket at the forward end adapted for receiving a hard, point of attack insert. The insert, which comprises tungsten cobalt, is coaxially aligned and is characterized having various sections: a nose section, a transitioning intermediate section adjacent to the nose section, and a base section. The nose portion of the insert typically has a rounded conical tip that extends to the diameter of the elongated intermediate section. The diameter of the intermediate section (d) is usually less than the diameter of the base section (D). The base of the hard alloy cap is shaped in such a way as to provide the tool with sufficient strength and durability for its intended operating conditions. A portion of the base section is brazed or otherwise affixed in the cavity at the forward end of the head portion. The cap has a height, H that extends from the front of the tip portion to a rear end of the base and the cap has a ratio of H:D is equal to or greater than 1.0, and a ratio of d:D is equal to or greater than 0.7.

U.S. Pat. No. 6,019,434 issued to Emmerich on Feb. 1, 2000 discloses a point attack bit having an enlarged head, an integral and coaxial shank extending from the base of the head, and a tip extending from the other end of the head and having a generally frusto-conical end with an odd number of side faces disposed between the end and the head.

U.S. Pat. No. 6,375,272 issued to Ojanen on Apr. 23, 2002 and describes a rotatable cutting tool for impinging the earth strata wherein the cutting tool has a tool body with an axial forward end and an axial rearward end. A hard insert is at the axial forward end and a retainer is carried by a shank portion near the axial rearward end. The hard insert has an axial forward generally conical tip section that presents a tip surface and has a starting included angle of between greater than about 110 degrees and less than about 140 degrees, a transition section (wherein at least a portion of the transition section presenting a convex shape) that is contiguous with and axially rearward of the tip section, a radially outwardly expanding first mediate section that is axially rearward of the convex section, and a base section that is axially rearward of the mediate section.

Accordingly, there is still a need in the industry to develop a rotating cutting bit that has reduced wear of the point attack insert so that down-time and operational costs are reduced and personnel safety improved.

SUMMARY OF THE INVENTION

Briefly, the present invention is an improvement on the rotational cutting bits used in road resurfacing preparations and more particularly an improvement on the point attack insert or tip that is received in a bore of these cutting bits. The point attack insert includes a head section; an axially aligned transitional intermediate section contiguous with the head section having a first diameter d and a sectional height H₁; and an axially aligned base section adjacent to the intermediate section having a second diameter D; wherein d:H₁ is greater than 1.0, wherein the ratio of d:D is from 0.62 to 0.68 and wherein the point attack insert has an overall height H and the ratio of H/D is less than 0.93.

In another embodiment of the present invention, the improved point attack insert includes: a head section having a generally conical shape with an apex and being of an axial length, the apex having an included angle A of greater than 110 degrees to about 140 degrees along the axial length of the head section; an axially aligned transitional intermediate section contiguous with the head section and having a first diameter d and a sectional height H₁; and an axially aligned base section adjacent to the intermediate section having a second diameter D; wherein d:H₁ is greater than 1.0, wherein the ratio of d:D is from 0.62 to 0.68, wherein the point attack insert has an overall height H and the ratio of H:D is less than 0.93.

In another embodiment of the invention, the improved point attack insert includes: a head section having a generally conical shape with an apex and being of an axial length, the apex having an included angle A of greater than 110 degrees to 140 degrees along the axial length of the head section; an axially aligned transitional intermediate section contiguous with the head section having a first diameter d and a sectional height H₁; and an axially aligned base section adjacent to the intermediate section having a second diameter D; wherein d:H₁ is greater than 1.0, wherein the ratio of d:D is from 0.62 to 0.68, wherein the point attack insert has an overall height H, and the ratio of H:D is less than 0.93, wherein at least a portion of the intermediate section has a generally frusto-conical configuration from the base section and having from 6 to 9 spaced apart side faces extending from the base section, each side face having side edges with adjacent side edges of adjacent side faces being adjoined, and the side faces collectively encircling the intermediate section and extending a portion of H₁.

Features and advantages of this invention will be apparent from the following detailed description of the preferred embodiments, appended claims and following brief description of the accompanying drawings.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a side view of a specific embodiment of a rotatable cutting tool illustrating in partial cross sectional view the mounted point of attack insert mounted in a bore or recess of a metal shank.

FIG. 2 is an enlarged side view of the point of attack insert.

DETAILED DESCRIPTION OF THE INVENTION

It is to be understood that the presently described point of attack insert of the invention is capable of many equivalent forms. While the drawings illustrate a preferred embodiment of such variations, and the specification describes a certain preferred embodiment thereof, such figures and description are by way of example only. There is no intent to limit the principles and scope of the invention to the particularly described embodiment but instead is to limited by the scope of the claims that follow.

As used herein, any relational term, such as “first”, “second”, “top” or “upper”, “bottom” or “lower”, and the like, is used for clarity and convenience in understanding the disclosure and accompanying drawings, and does not connote or depend on any specific preference, orientation, or order, except where the context clearly indicates otherwise.

As used herein, the terms “about” and “substantially” in reference to a given parameter, property, or condition means that the given parameter, property, or condition is met with a small degree of variance such as within acceptable manufacturing tolerances and generally includes a variability of up to 5% of the designated value. For example, a term of “about 1.0” would include a variable range of from 0.95 to 1.05.

Referring to FIG. 1 in greater detail, a rotational cutting bit utilized for road planing is denoted as 5. The cutting bit 5 typically includes a shank portion 6 which is adapted to be inserted into and retained in the rotating cutter drum of the road planing machine. Typically, such cutting bits when directed for road planing operations have shanks with an overall diameter of about 19.4 millimeters (mm). The cutting bit also includes an exposed portion 7 contiguous with the shank portion 6. At a forward end, the exposed portion 7 includes a recess or bore 8 of a predetermined geometry and depth for affixing a point attack insert or tip 10 to the exposed portion 7.

The art is replete with descriptions, configurations, and variations on a cutting bit, their respective shanks and exposed portions. For example, U.S. Pat. No. 7,959,234 B2 issued to Cameron et al. on Jun. 14, 2011, in column 5 lines 1-51, the description of which is incorporated herein by reference, provides in greater detail one rendition of such cutting bits, the use and purpose of a retainer clip and the washer encircling the shank. The same may be said as too the methods of affixing the point attack insert 10 to the exposed portion 7, as are methods of making and using a rotational cutting bit. Being well known to those skilled in the area of road resurfacing (planing) operations, further description of the shank 6 and exposed portion 7 and use of the bit 5 are unnecessary for the understanding of the present invention.

Referring to FIGS. 1 and 2, the point attack insert 10 comprises a plurality of sections substantially coaxially aligned with the shank 6 and exposed portion 7. The sections include: a head section 20; a transitional intermediate section 30 contiguous with the head section 20; and a base section 40 adjacent to the intermediate section.

Referring to FIG. 2, the head section 20 has a generally conical configuration having an apex or tip 22 that, desirably, is rounded to promote impact strength. The head section 20 tapers outwardly and generally downwardly in an axial direction from the apex 22, i.e., toward the base 40, at an included angle, A, of from 80 degrees to about 140 degrees, or in another embodiment from about 90 degrees to 140 degrees, or more desirably, in another embodiment from 110 degrees to 140 degrees. The head section 20 can have a height of from a 2 mm to about 10 mm, or from 3 mm to 7 mm, or from 4 mm to 6 mm, depending upon the diameter d, the apex 22 radius, and the angle A. Desirably, in one embodiment the angle A is from 120 degrees to about 140 degrees and the head section 20 has a height of from about 3.5 mm to 5.5 mm.

The intermediate transitional section 30 has a first diameter, d, determined at a juncture 24 of the head section 20 and the intermediate section 30, of from about 0.49 inch (12.4 mm) to about 0.62 inch (15.8 mm), or in another embodiment from about 0.53 inch (13.5 mm) to about 0.56 inch (14.2 mm), or more desirably from 0.50 inch (12.7 mm) to about 0.53 inch (13.5 mm). The transitional intermediate section 30 extends downwardly along a longitudinal direction to the juncture 46 of the base section 40. The intermediate section 30 has a height, H₁, of about 9 mm to 15 mm, or in another embodiment of from about 11 mm to about 14 mm, or more desirably from about 12 mm to about 14 mm.

In accordance with the present invention, the intermediate section 30 has a ratio of the first diameter d to the sectional height H₁ that is greater than 1.0. In another embodiment, the ratio of d:H₁ is from 1.02 to 1.40, or in another embodiment from 1.02 to 1.25, or in yet another embodiment from 1.02 to 1.05. Surprisingly, it has been found that an intermediate section 30 having a ratio of d:H₁ greater than 1 gives superior heat transfer attributes to the insert 10 in comparison to inserts wherein the ratio of the diameter to height is equal to or less than 1.0. Advantageously, the insert of the present invention provides a longer duration that a cutting bit can be utilized without necessitating stopping operations and change-out.

In yet another embodiment, the transitional intermediate section 30 has a generally frusto-conical shape that radially tapers outwardly to the base section 40. The taper of the frusto-conical shape can have a radius of curvature equal to or is greater than 0.100 of an inch (2.54 mm), or alternatively is greater than 0.150 of an inch (3.81 mm), and more desirably is from 0.250 (6.35 mm) to 0.500 of an inch (12.7 mm). The intermediate section 30 has a maximum first diameter d that is less than the second diameter D of the base section 40.

The base section 40 is contiguous and coaxially aligned with the intermediate section 30. The base section 40 has a second diameter, D that is greater than the first diameter, d, and has a circumference that is slightly less than an inside edge of the recess or bore 8. The open space created by this difference is necessary so that when the insert 10 is positioned in the bore 8 and brazed into position, a portion of the braze flows over and around the base 40. Desirably, the base 40 includes a plurality of protuberances 47 that purposefully elevate the base portion 40 a predetermined distance to facilitate allowing the brazing to evenly flow below and around the base 40.

The base section 40 has a predetermined height or thickness, T, determined by the distance between a bottom edge 44 and a top edge 46 of the base 40. The thickness or height, T, of the base 40 is such that the top edge 46 may be a from 0.001 to 0.100 of an inch below or substantially level, i.e., plus or minus 0.020 of an inch variance from the top of bore 8 when the insert 10 is brazed to the exposed portion 7. The base section 40 can have a sectional height of from about 0.76 mm to about 2.30 mm, and more desirably in another embodiment from about 1.0 mm to about 2.0 mm.

The point attack insert has a total height, H, that is less than the second diameter D, so that the ratio of H:D is less than 0.93, or in another embodiment is from 0.75 to 0.93, or in another embodiment from 0.78 to 0.92, or from 0.82 to 0.90, or in another embodiment is from 0.85 to 0.89.

Continuing reference to FIG. 2, the present invention the insert 10 optionally includes a plurality of space apart side faces 50 extending upwardly from the base section 40. Each side face 50 includes side edges 52 with adjacent side edges of adjacent side faces being adjoined. The side faces 50 are disposed symmetrically about the axis of the insert 10 collectively encircling a portion of the intermediate section 30. The numbers of side faces 50, while symmetrical about the axis of the insert 10, are disposed from the base section 40 and upwardly encircling a portion of the intermediate section 30 forming a generally frusto-conical configuration. The number of side faces 50 encircling the base and a portion of the intermediate sections, 40 and 30, respectively, can be from 5 to 12, or in another embodiment from 5 to 10, or in a more desirable embodiment, from 6 to 9. The faces 50 may be substantially flat or they may be arcuate.

The side faces 50 extend upwardly (i.e., toward the head section 20), only partly of the intermediate section 30 sectional height, H₁. In one embodiment, the side faces 50 extend from 10 to 90 percent of the sectional height, H₁. In another embodiment, the side faces 50 extend from 10 to 80 percent of the sectional height, H₁. In yet another embodiment, the side faces 50 extend from 10 to 60 percent of the sectional height, H₁.

The insert 10 is typically single monolithic piece made from a cemented carbide material such as, for example, a cobalt-tungsten carbide alloy, formed by conventional powder metallurgical techniques. Although the specific grade of cemented carbide depends upon the particular application for the cutting tool, rotatable cutting tools used in road planing applications may use a hard insert made of cobalt cemented tungsten carbide wherein the cobalt content ranges between about 5.5 weight percent to 6.5 weight percent with the balance comprising extra coarse tungsten carbide. The hardness of the cemented tungsten carbide may range between about 86 and about 90.4 Rockwell A. A preferred grade of cemented tungsten carbide for a road planing application has a cobalt content that ranges between about 5.2 weight 8 percent and about 6.3 weight percent with the balance being essentially tungsten carbide and the hardness ranging between 87.5 and 88.5 Rockwell A.

The hard inserts 10 are typically brazed in the socket or recess 8 of the cutting tool body. The specific braze alloy may vary depending upon the particular application. One exemplary braze alloy include copper-zinc-nickel-manganese-silicon braze alloys sold by Handy & Harman, Inc. 859 Third Avenue, New York, N.Y. 10022 under the designations HI TEMP 080 and HI-TEMP 548. U.S. Pat. No. 5,219,209 to Prizzi et al. sets forth a more detailed description of this braze alloy. Two other exemplary braze alloys for road planing applications are disclosed in U.S. Pat. No. 4,389,074 comprise either Nicumn 23 or Nicumn 37 each of which are sold by Wesgo. The composition of Nicumn 23 in weight percent is 67.5 percent copper, 23.5 percent manganese, and 9 percent nickel. The composition of Nicumn 37 (ASTM-4764) in weight percent is 52.5 percent copper, 38 percent manganese, and 9.5 percent nickel.

The present invention is illustrated in greater detail by the specific example presented below. It is to be understood that this example is an illustrative embodiment and is not intended to be limiting of the invention, but rather are to be construed broadly within the scope and content of the appended claims.

Example

A Wirtgen W200i road planing machine having a 7-foot wide milling drum with 279 tool holding positions was utilized to plane approximately 2.0 lane miles of asphalt road surface in Mississippi. The depth of cut was 1.5 inches. The milling drum was outfitted with: a) 140 cutting bits having a point attack insert in accordance with the present invention having a diameter of 12.7 mm and a height H₁ of 12.4 mm giving a ratio of d:H₁ of 1.02; and b) 139 cutting bits of a commercially available product having a diameter d of 11.5 mm and a height H₁ of 13.5 mm giving a d:H₁ ratio of 0.85.

At the end of the test, the cutting bits were removed from the milling drum. The results are presented in Table 1 below.

TABLE 1 Present Insert Commercial tool Initial tip weight 40 grams 48.5 grams Avg. height reduction 0.30 inch 0.44 inch Calculated Total weight lost grams 14.5 17.2 d:H₁ 1.02 0.85 Q/t factor* 10.64 5.94 *Q/t = kA(T₂ − T₁)/d. See https://study.com/academy/lesson/heat-transfer-through-conduction-equation-examples.html.

As can be seen from this example, the present invention provided excellent wear attributes. This was surprising since the commercial product had a greater mass and a taller intermediate section.

Having described the invention in detail, those skilled in the art will appreciate that modifications may be made to the various aspects of the invention without departing from the scope and spirit of the invention disclosed and described herein. It is, therefore, not intended that the scope of the invention be limited to the specific embodiments illustrated and described but rather it is intended that the scope of the present invention be determined by the appended claims and their equivalents. Moreover, it is to be understood, that the ranges provided herein are inclusive not only of those specifically enumerated, but also all ranges in between. All patents, patent applications, publications, and literature references presented herein are incorporated by reference in their entirety for any disclosure pertinent to the practice of this invention. 

What is claimed is:
 1. In a rotating cutting bit utilized in a road resurfacing machine, wherein the cutting bit includes a metal shank adapted to be mated with a resurfacing drum and a forward end, wherein the forward end includes a bore or recess that is adapted to fixedly receive at least a portion of a point attack insert wherein the improvement comprises: a point attack insert comprising a head section; an axially aligned transitional intermediate section contiguous with the head section having a first diameter d and a sectional height H₁; and an axially aligned base section adjacent to the intermediate section having a second diameter D; wherein d:H₁ is greater than 1.0, wherein the ratio of d:D is from 0.62 to 0.68, wherein the point attack insert has an overall height H and the ratio of H:D is less than 0.93.
 2. The point attack insert of claim 1 wherein said ratio of H:D is from 0.75 to 0.93.
 3. The point attack insert of claim 2 wherein said ratio of H:D is from 0.78 to 0.92.
 4. The point attack insert of claim 3 wherein said ratio of H:D is from 0.82 to 0.90
 5. The point attack insert of claim 4 wherein said ratio of H:D is from 0.85 to 0.89.
 6. The point attack insert of claim 1 wherein said ratio of d:H₁ is from 1.02 to 1.40.
 7. The point attack insert of claim 6 wherein said ratio of d:H₁ is from 1.02 to 1.25.
 8. The point attack insert of claim 7 wherein said ratio of d:H₁ is from 1.02 to 1.05.
 9. The point attack insert of claim 1 wherein said head section has a generally conical shape with an apex and being of an axial length, the apex having a starting included angle of greater than about 88 degrees to about 140 degrees along the axial length of the head section, and wherein at least a portion of the intermediate section having a generally frusto-conical configuration from the base section and having a plurality of spaced apart side faces extending from the base section, each side face having side edges with adjacent side edges of adjacent side faces being adjoined, and the side faces collectively encircling the intermediate section and extending a portion of H₁.
 10. The point attack insert of claim 9 wherein said angle is from 110 degrees to 140 degrees.
 11. The point attack insert of claim 10 wherein said angle is from 120 degrees to 140 degrees.
 12. The point attack insert of claim 9 having from 5 to 12 side faces.
 13. The point attack insert of claim 9 having from 5 to 10 side faces.
 14. The point attack insert of claim 9 having from 6 to 9 side faces.
 15. The point attack insert of claim 9, 12, 13 or 14 wherein each side face is arcuate.
 16. In a rotating cutting bit utilized in a road resurfacing machine, wherein the cutting bit includes a metal shank adapted to be mated with a resurfacing drum and a forward end, wherein the forward end includes a bore or recess that is adapted to fixedly receive at least a portion of a point attack insert wherein the improvement comprises: a point attack insert comprising a head section having a generally conical shape with an apex and being of an axial length, the apex having an included angle A of greater than 110 degrees to about 140 degrees along the axial length of the head section; an axially aligned transitional intermediate section contiguous with the head section having a first diameter, d, and a sectional height H₁; and an axially aligned base section adjacent to the intermediate section having a second diameter D; wherein d:H₁ is greater than 1.0, wherein the ratio of d:D is from 0.62 to 0.68, wherein the point attack insert has an overall height H and the ratio of H:D is less than 0.93.
 17. The point attack insert of claim 16 wherein at least a portion of said intermediate section having a generally frusto-conical configuration from the base section and having a plurality of spaced apart side faces extending from the base section, each side face having side edges with adjacent side edges of adjacent side faces being adjoined, and the side faces collectively encircling the intermediate section and extending a portion of H₁.
 18. The point attack insert of claim 16 wherein said ratio of H:D is from 0.75 to 0.93.
 19. The point attack insert of claim 18 wherein said ratio of H:D is from 0.82 to 0.90
 20. The point attack insert of claim 19 wherein said ratio of H:D is from 0.85 to 0.89.
 21. The point attack insert of claim 16 wherein said ratio of d:H₁ is from 1.02 to 1.25.
 22. The point attack insert of claim 21 wherein said ratio of d:H₁ is from 1.02 to 1.05.
 23. The point attack insert of claim 16 wherein said angle is from 120 degrees to 140 degrees.
 24. The point attack insert of claim 17 having from 6 to 9 side faces.
 25. The point attack insert of claim 24 wherein each side face is arcuate.
 26. In a rotating cutting bit utilized in a road resurfacing machine, wherein the cutting bit includes a metal shank adapted to be mated with a resurfacing drum and a forward end, wherein the forward end includes a bore or recess that is adapted to fixedly receive at least a portion of a point attack insert wherein the improvement comprises: a point attack insert comprising a head section having a generally conical shape with an apex and being of an axial length, the apex having an included angle, A, of greater than 110 degrees to 140 degrees along the axial length of the head section; an axially aligned transitional intermediate section contiguous with the head section having a first diameter, d, and a sectional height H₁; and an axially aligned base section adjacent to the intermediate section having a second diameter D; wherein d:H₁ is greater than 1.0, wherein the ratio of d:D is from 0.62 to 0.68, wherein the point attack insert has an overall height H, and the ratio of H:D is less than 0.93 and wherein at least a portion of said intermediate section having a generally frusto-conical configuration from the base section and having from 6 to 9 spaced apart side faces extending from the base section, each side face having side edges with adjacent side edges of adjacent side faces being adjoined, and the side faces collectively encircling the intermediate section and extending a portion of H₁.
 27. The point attack insert of claim 26 wherein each side face is arcuate.
 28. The point attack insert of claim 26 wherein said ratio of H:D is from 0.85 to 0.89.
 29. The point attack insert of claim 26 wherein said ratio of d:H₁ is from 1.02 to 1.25.
 30. The point attack insert of claim 29 wherein said ratio of d:H₁ is from 1.02 to 1.05.
 31. The point attack insert of claim 9, 17 or 26 wherein said side faces extend from 10 to 90 percent of H₁. 